A New Isosporan (Apicomplexa: Eimeriidae) from the Pacific Blue-Tailed Skink, Emoia caeruleocauda (Sauria: Scincidae: Eugongylinae), from Guam, U.S. Territory.

Abstract

Purpose: Nothing is known about coccidians (Apicomplexa: Eimeriidae) from the Pacific blue-tailed skink, Emoia caeruleocauda. Here, we report mensural and morphometric data on a new species of Isospora from E. caeruleocauda from Guam, US Territory.

Methods: Feces from four E. caeruleocauda collected by hand in November 2023 were placed in individual vials containing 2.5% potassium dichromate. They were examined for sporulated oocysts after flotation in Sheather's sugar solution, measured, and photographed.

Results: A single (25%) E. caeruleocauda was found to be passing oocysts representing a new species of Isospora. Oocysts of Isospora guamensis n. sp. are ellipsoidal to ovoidal with a bi-layered wall, measure (L × W) 16.5 × 11.8 μm, and have a length/width (L/W) ratio of 1.4; a micropyle and an oocyst residuum were absent but a polar granule was present. Sporocysts are ovoidal and measure 9.4 × 6.5 μm, L/W 1.4; Stieda and sub-Stieda bodies were present but a para-Stieda body was absent. The sporocyst residuum is composed various-sized granules in a compact rounded or irregular mass, sometimes dispersed between the sporozoites. The new species can be differentiated from all other isosporans from skinks by possessing the smallest oocysts known from this host family.

Conclusion: This is the first time an isosporan coccidian has been reported from E. caeruleocauda as well as the first report of a coccidian from a Guam-inhabiting skink.